[1] Kyung Hee Univ, Dept Neurol, Coll Med, Seoul, South Korea
[2] Ewha Womans Univ, Coll Med, Dept Neurol, Seoul Hosp, Seoul, South Korea
[3] Soonchunhyang Univ, Cheonan Hosp, Coll Med, Dept Radiol, Cheonan, South Korea
[4] Catholic Univ Korea, Eunpyeong St Marys Hosp, Dept Radiol, Seoul, South Korea
[5] Soonchunhyang Univ, Coll Med, Dept Neurol, Sleep Disorders Ctr,Cheonan Hosp, 31 Suncheonhyang 6 Gil, Cheonan 31151, South Korea